Overview of Valley Types Formed by Göksu River (Mersin, Southern Turkey)

Abstract

There are varius valley types in the rock groups formed from Ordovician to Miocene at the mouth of the Göksu River. Basement rocks in the area are coposed of mainly low resistant Miocene mudstone-shale-marl and high resistant chalkarenites and an important or lesser amount of low resistant Ordovician metamorfic rocks; medium to high resistant Upper Devonian-Upper Cretaceous clastic and carbonateceous rocks. The types of valley with wide and gentlement floor (broad valley) is dominant in the Langhian- Tortonian low resistant mudstone-shale-marl-clayey limestone in the Mut and surrounding area. These rock groups have cropped out in the ondulated morphology and as low dipping stratas. The deposition of the thick alluvial materials in the bottom of the Göksu River caused the developing of the many small scale planes along the Göksu Valley. A canyon valley in 2.5 km long was also developed in the Miocene chalcarenites showing plentiful joints and strongly porous nature that were observed in the Evkafçiftliği and Kargıcak villages, in the central part of the study area. A very thin alluvial cover composed of pebles-sands and muds was deposited at the bottom of the canyon. The valleys developed on the Paleozoic-Mesozoic clastic and carbonateceous rocks in the main valley of the Göksu River at the surrounding area of the Değirmendere and Karakaya villages in the western part of the Silifke are narrow floor, anticline and cutting through type valleys. Terrace deposits are clearly observed in the main valley slopes while recent alluvial materials deposited in the bottom of the valley are in the shape of narrow and thin strips. The meander valley types can distinctly be distinguished in the Langhian-Tortonian mudstones-shales- marls and very wide spread and very thick Holocene alluviums of the Göksu delta at the center of the Silfke and surrounding area in the eastern-south-eastern part of the study area.